Download the 10.3.9 combo update from apple here:
[http://support.apple.com/kb/DL496]
This will update ALL previous Panther versions up to the latest OS which is 10.3.9 this will save you alot of time from updating it one version at a time.
This update will most likely update the itunes as well then once you have finished the update go to the apple menu on the top left and run SOFTWARE UPDATE. This will find and install any further firmware that was released after the combo update pack. Just keep running the software update until it does not find anymore new firmware versions.